In the field of semiconductor wafer processing it is common practice to subject the semiconductor wafer to etching processes to remove a portion of a multi-layer device. The etching process is frequently quite sensitive to slight variations in temperature of the etching solution. Various types of wet etching processes and wet etching apparatus are used in the semiconductor wafer processing art to fabricate microelectronic integrated circuits. In the semiconductor wafer processing art devices are formed by depositing and etching integrated circuit components in multiple layers. Both wet and dry etching processes are used where a portion of a material layer is removed as part of the process to fabricate a feature or component of a semiconductor device. In both wet and dry processes, it is critical to remove material uniformly across the semiconductor wafer surface to maintain critical dimensions (CD) of the patterned structures and to avoid compromising subsequent processes such as photolithographic patterning processes. For example, where an etching process preferentially etches a portion of the wafer surface, semiconductor device structures are formed with CD's unacceptably outside of design specifications leading to costly rejection of the process wafer for subsequent processing.
For example, one type of wet etching process is spin wet etching where a single process wafer is mounted on a rotatable platen and rotated at high angular velocity while being contacted with a wet etching solution, for example by spraying the wet etching solution onto the wafer process surface. For example, following a dry etching process according to an overlying photolithographically patterned photoresist layer and following an ashing process to remove a portion of the photoresist layer, remaining ashing resistant photoresist polymeric residues are removed by a single wafer wet spin etching process. Several semiconductor wafer manufacturing processes likewise advantageously use a single wafer wet spin etching process to remove a portion of a material layer as the process may offer better control in terms of etching rates and etching uniformity.
In many single wafer wet spin etching processes, the temperature of the etching solution is critical since relatively small changes in the wet etching solution temperature may have a large impact on etching rates and fluid viscosities which are critical in a spin process. Since a single wafer wet spin etching process is typically optimized at a predetermined wafer spin rate and etching solution temperature where the etching process is carried out for predetermined time periods, changes in the etching solution temperature outside of process design constraints may lead to non-uniform etching including overetching or underetching of the process surface.
In a single wafer wet spin etching process according to the prior art, following a period of idleness or non-use it is necessary to operate the etcher for a period of time to bring the etching solution up to an operating delivery temperature. For example single wafer wet spin etchers of the prior art typically include an etching solution holding tank, a fluid pump and a heat exchanger in the etching solution flow pathway prior to delivery to the wet etching solution dispenser. Following a period of idleness, according to prior art processes, the single wafer wet spin etcher is operated for a warmup time period, for example by including a dummy wafer in the etcher, in order to bring the etching solution up to an appropriate operating temperature.
Frequently process tools included in a semiconductor manufacturing line, for example, including temperature dependent solution delivery systems for operating the tool, for example, single wafer wet spin etchers, have intervening periods of idleness or non-productive time. Following periods during which upstream manufacturing processes are either delayed or slowed, the solution delivery system is frequently put into a state of idleness to lower production costs. As a result, following the period of idleness, a warmup time period to bring the tool including a solution delivery system up to operating temperature further adds to non-productive time and thereby impairs the tools productive operating efficiency. Frequently, the required warmup time period is ill-defined since periods of idleness are unpredictable. In addition, it is prohibitively costly in terms of energy use and machine wear if the tools are continuously operated to preserve an operating temperature. As a result, temperature dependent fluid delivery system tools frequently have poor operating efficiencies, including delaying downstream production processes.
Thus, there is a need in the semiconductor device manufacturing art for a method and apparatus for improving the operating efficiency of temperature dependent process tools including solution delivery systems to reduce a startup processing time to increase tool operating efficiencies.
It is therefore an object of the invention to provide a method and apparatus for improving the operating efficiency of temperature dependent process tools including solution delivery systems to reduce a startup processing time to increase tool operating efficiencies while overcoming other shortcomings and deficiencies of the prior art.